This type of conventional technology is disclosed in Patent Literature 1. This conventional technology is a construction machine such as a hydraulic excavator, and in order to easily and reliably perform mounting work of a vibrationproof member of a post-treatment device, electric wiring work, and the like, which require time and labor, a post-treatment device assembly is configured by a support member composed of a separate member from a vehicle body, and a post-treatment device assembled to the support member through the vibrationproof member, and this post-treatment device assembly is mounted on the vehicle body by using the support member.